Shares of the three big US wireless carriers fell after a report that SpaceX wants access to tens of thousands of cell sites, Forbes and Reuters reported.

Bloomberg reported Thursday that SpaceX is in talks with tower companies to secure access to at least 80,000 sites across the United States, according to Reuters. Bloomberg cited people familiar with the matter. SpaceX has held talks with at least one of the largest tower owners, Crown Castle, Forbes said, citing Bloomberg. No deal has been confirmed.

Crown Castle, American Tower, Vertical Bridge and SpaceX did not immediately respond to Reuters requests for comment. Chris Hillabrant, Crown Castle's CEO, was asked on an earnings call whether the company had talked about leasing towers to satellite firms. "You can assume that we're talking to all parties," he said, according to Forbes.

In premarket trading early Friday, AT&T fell 3.74% to $21.89, Verizon fell 3.25% to $43.73 and T-Mobile fell 3.13% to $153.82, Forbes reported. Crown Castle rose 7.31%, and SpaceX was up 3.07% to $149.19 after falling 9.14% on Thursday, Forbes said. In extended trading Thursday, carrier shares had fallen between 4.2% and 5%, Reuters reported.

The deals could help SpaceX build a fourth national wireless carrier, Reuters said. Elon Musk confirmed plans for a ground-based wireless network on an earnings call Tuesday, Forbes reported. He said Starlink would "ultimately be a business that generates several hundred billion dollars in revenue a year," Forbes said. He gave no timeline.

The 80,000 sites would equal half of the 158,500 cell towers in the US last year, Reuters said, citing the Wireless Infrastructure Association. Crown Castle runs about 40,000 US towers and American Tower about 42,000 sites, Reuters said. Vertical Bridge, which is privately held, owns about 18,000.

A nationwide ground network would cost more than $80 billion and take many years, TD Cowen estimated, according to Reuters. SpaceX agreed this month to buy low-band spectrum from Grain Management, a deal that still needs FCC approval, Forbes reported.

What we know: Bloomberg reported the talks, and carrier stocks fell in early trading on the news.
What we don't: Whether any tower company will sign a deal with SpaceX, or on what terms.